1. Field of the Invention
This invention relates to a content distribution system, a content distribution method and a terminal device, and more particularly, is suitably applied to a content distribution system using the Internet or the like.
2. Description of the Related Art
In a content distribution system of this kind, a distribution server distributes data (hereinafter, referred to as content) to a requesting user's personal terminal out of many personal terminals connected to the server through a network such as the Internet, the content composed of material data such as text, video and audio based on a scenario.
At this time, such a cipher system is generally adapted that the distribution server encrypts the content before transmission and the user's personal terminal is allowed to display the content only when it can decrypt the encrypted content received through the network.
In the content distribution system adapting such cipher system, however, a user views content after decryption, so that if the content stored on the hard disk or in an external memory of his/her personal terminal is taken out to the outside, or if the content is published over the network, the content can be illegally copied and it is difficult to prevent such data leakage.
Even if illegally-copied content or content which is illegally published over the network is detected, it is difficult to find a person which illegally obtained the content and to certify the identity of the content. Therefore, to prevent this illegal data leakage, some actions beyond legal regulations should be done.
In addition, because easy digital copy can create content which is completely the same as the original, what we can do is to strictly protect copyright. As a result, users should follow more strict usage rule than before, and more users who formally bought content are not satisfied with the rule.